1. Field of the Invention
The present invention relates to a lens barrel supporting frame, a lens retaining structure, a lens barrel and a camera, and in particular, relates to a lens barrel having a plurality of supporting frames.
2. Description of the Related Art
Digital cameras that make use of image sensors such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal-oxide Semiconductor) sensor to convert an optical image into an electrical signal, and record by digitizing the electrical signal, have grown to be popular in recent years.
With these digital cameras, there is a need not only for increasing the number of pixels of the CCD or CMOS sensor, but also for improving the performance of the lens barrel that forms the optical image on the image sensor. More specifically, there is a need for a lens barrel equipped with a high-power zoom lens system.
On the other hand, the body of digital cameras needs to be made more compact in order to improve the portability. To this end, the lens barrel is required to be miniaturized, which is thought to largely contribute to the miniaturization of the body.
Consequently, for example, as disclosed in Japanese Patent Laid-Open Publication Nos. JPH7-191249, JP2002-277709, JP2005-234259, and JP2006-133682, various lens barrels have been proposed before.
However, with a conventional lens barrel, further miniaturization is difficult.
For example, with the lens barrel disclosed in JPH7-191249, a first zoom frame 31 supporting a first lens group L1 which is closest to the subject is supported to be moveable in the direction along the optical axis by a stationary frame 34. In this case, in order to miniaturize the lens barrel, it is necessary to further reduce the sizes of the stationary frame 34 and the first zoom frame 31 in the direction along the optical axis.
In addition, with the lens barrel disclosed in JP2002-277709, a cam frame 15 is supported to be movable in the direction along the optical axis by a stationary frame 13. A first group movement frame 18 supporting the first lens group L1 is supported to be movable in the direction along the optical axis by the cam frame 15. In this case, in order to miniaturize the lens barrel, it is necessary to further reduce the sizes of stationary frame 13, the cam frame 15, and the first group movement frame 18 in the direction along the optical axis.
However, as FIG. 5 of JPH7-191249 and FIG. 5 of JP2002-277709 make clear, with both the lens barrels, it is difficult to further reduce the sizes of the members.
In addition, a lens barrier is disposed to cover the first lens group in a conventional lens barrel. Generally, a lens barrier is fixed to the first lens frame that retains the first lens group, and includes a barrier mechanism for protecting the first lens group, and an operating lever for switching the barrier mechanism open or close. It is possible to switch the barrier mechanism open or close by moving the operating lever in the rotational direction around the optical axis. A drive lever for driving the operating lever is disposed on a motionless member such as a master flange. When the lens barrier moves in the direction along the optical axis relative to the motionless member, the operating lever is driven by the drive lever in the rotational direction and the direction along the optical axis.
For example, with the lens barrel disclosed in JP2006-133682, when an engagement portion 7d of a barrier drive frame 7 and a stationary member 12 relatively move in the direction along the optical axis, a tapered surface of the engagement portion 7d and a sloped surface 12a of the stationary member 12 slide together. As a result, the barrier drive frame 7 and the stationary member 12 relatively move in the rotational direction, and opening and closing operation of a barrier 4 is switched.
However, since the lens barrier is a mechanism for covering the first lens group, the lens barrier is fixed to a tip portion of the first lens frame supporting the first lens group. Meanwhile, the master flange provided with the drive lever is disposed on the farthest position from the subject in the lens barrel. In other words, a plurality of supporting frames are generally disposed between the lens barrier and the master flange. Consequently, with the lens barrel disclosed in JP2006-133682, in order to drive the engagement portion 7d of the barrier drive frame 7 via the stationary member 12, for example, it is necessary to provide an opening through which the engagement portion 7d and the stationary member 12 pass in the direction along the optical axis in another supporting frame. As a result, the design freedom of each supporting frame deteriorates, and the miniaturization of the lens barrel is hindered.
In addition, with a conventional lens barrel, a cam portion causes the outside dimension of the cylindrical portion of the supporting frame to be larger. For example, with the lens barrel disclosed in JP2005-234259, three cam followers 17a are disposed on the outer periphery side of a lens frame 17. The cam followers 17a are inserted into a cam groove 13b formed on the inner periphery part of a drive tube 13. When the lens frame 17 rotates relative to the drive tube 13, the lens frame 17 moves relative to the drive tube 13 in a direction along the optical axis. At this time, since a load acts on the cam followers 17a, the portion on which the cam followers 17a are formed is thicker compared to the surroundings thereof in the lens frame 17, as shown in FIG. 1 of JP2005-234259. As a result, even if the surroundings is thinner, the outside dimension of the lens frame 17 becomes larger due to the portion on which the cam followers 17a are formed, and the miniaturization of the lens barrel is hindered.
In addition, in a conventional lens barrel, since three cam portions and three cam grooves are disposed at a constant pitch in the circumferential direction, the supporting frames may be attached in a wrong direction when fixing a supporting frame to another supporting frame. Such assembly performance deterioration causes the assembly time to increase, and sometimes causes the yield of the product to decrease. As a result, the manufacturing cost of the lens barrel increases.
Furthermore, in a conventional lens barrel, since a supporting frame is supported by three cam portions and three cam grooves, if an impact is applied to the lens barrel when a user drops the camera, the cam portions and the cam grooves may be damaged.